This is really an interesting and decent student you have.

In this situation, you could only appeal to his "intuition" and perhaps also his creative mind by showing him the numbers in the written form (Arabic ciphers) and draw strokes (1 stroke for "1", 2 for "2", etc.) next to this cipher. If you can manage and if he is able to, have him imitate the English pronunciation for the numbers. Deaf people sometimes can read from the lips. I do not know if your student really can.

I have dealt with a deaf priest from Switzerland before - he actually could drive a car, was more or less fluent in three foreign languages in addition to his native language. This requires special education provided to deaf people. In your case, I do not know whether that would be possible your student.

Perhaps you would also think about getting some expert advice from qualified people trained to teach deaf people.

Good luck!